Power tube



w. T. GIBSON POWER TUBE Filed Aug. 1, 1928 Patented Sept. 5, 1933 UNITED STATES PATENT OFFICE POWER TUBE William T. Gibson, Aldwych, London, England,

assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application August 1, 1928, Serial No. 296,776, and in Great Britain August 27, 1927 2 Claims.

the limiting factors in the design this kind when used for very short of tubes of Wave work is the dielectric loss which occurs at these frequencies in the vitreous material 0 f the envelope, for instance, in a tube consuming 10 kilowatts and operating at wave lengths of say 25 meters or less the field between the grid and filament causes dielectric loss in t the stem which leads to heating and cracking of the glass.

he glass of electrolysis To a certain extent this defect may be mitigated by using material such as Pyrex glass, but even so it is not possible to go far beyond wave lengths of 25 meters without the glass being in danger of fracture.

lar and the filament seals.

A better understanding of the invention will be obtained by referring to the ac drawing, which gives a fragmentary electron discharge device of the type In the drawing 1 represents a vit companying View of an referred to. reous vessel which is fused on to an external anode portion 2. The vessel is provided with a ire-entrant stem 3 which is frictionally engaged by a metal collar 4 from which is suspended the grid supporting structure 5. A grid lead-in conductor 6 is connected to the collar 4 and passes out along the laterally disposed tubular portion 7 and through the copper seal 8.

The filament leads 9 pass through two externally projecting members 10, which according to the invention are made as long as conveniently possible, so that the metal seals 11 are arranged as far as possible from the grid collar 4, thus causing the gl ass leakage path to be extended and the field in the glass decreased. A further central tubular portion 12,

preferably of glass, is suspended from the top of the vessel and carries at its lower collar 13 from which the filament structure 14 is borne.

end a metal supporting According to the invention the losses in the re-entrant tube 3 are avoided by providing it with a guard ring 15 on the inside.

This may consist of copper gauze, or sheet-nickel bent around and expanded into position and conductively connected to the grid collar, for instance,

as shown at 16. The result is that the inside and outside of the glass tube 3 are maintained at the same potential and all field is removed from. this portion of the glass, the grid filament field being located primarily in vacuum.

Thus, the dielectric losses occurring at high frequencies are eliminated from the vitreous material of the envelope and it is possible to operate the device at very short wave lengths Without any damage being done thereto.

What is claimed is:

1. An electron discharge device comprising an enclosing vessel having a metallic anode portion and a glass portion, said glass portion being provided with a reentrant tubular member, a metallic collar in contact with one surface of said tubular member, a grid supported by said collar and extending into said anode portion, a leading-in conductor between said vessel and tubular member and connected to said collar, a cathode within said grid, leading-in conductors for said cathode Within said tubular member, and a metallic shield in contact with the inner surface of said tubular member and conductively connected to said collar around the internal edge of said tubular member, said shield being located between said cathode leading-in conductors and said grid leading-in conductor.

2. An electron discharge device comprising an enclosin vessel having a metallic anode portion and a glass portion, said glass portion being provided with inner and outer reentrant stems, said outer stem being of cylindrical formation, a cathode assembly supported by said inner stem, leading-in conductors for said cathode extending between said inner and outer stems, a metallic collar engaging the outer surface of the cylindrical outer stem, a grid supported by said collar and located between said cathode and anode, a leading-in conductor for said grid attached to said collar and located between said outer stern and said vessel, a cylindrical metallic guard ring engaging the inner surface of said outer cylindrical stem, and an electrical connection around the edge of said cylindrical stem joining said collar and ring together.

WILLIAM T. GIBSON. 

